In this study, we investigated an ammonia (NH 3) plasma-pretreatment (PT) for suppressing the formation of interface states between metal nanocrystals (NCs) and the surrounding dielectric during the NC forming process with the aim of obtaining a highly reliable Pd NC memory. The discharge-based multipulse (DMP) technique was performed to analyze the distribution of trap energy levels in the Pd NCs/Si 3N 4-stacked storage layer. Through DMP analysis, it is confirmed that the NH 3 PT not only significantly increases the quality of the surrounding dielectric of metal NCs but also effectively passivates shallow trap sites in the Si 3N 4 trapping layer. As compared with the sample without NH 3 PT, the NH 3-plasmatreated device exhibits better reliability characteristics such as excellent charge retention (only 5% charge loss for 104 s retention time) and very high endurance (no memory window narrowing after 105 program/erase cycles). In addition, the robust multilevel cell retention properties of the NH 3-plasma-treated memory are also demonstrated.